1. Field of the Invention
The present invention relates to an electromechanical transducer such as a capacitive electromechanical transducer for use as an ultrasonic transducer or the like, and to a method of manufacturing such an electromechanical transducer.
2. Description of the Related Art
Micromachining technology has made possible micrometer-scale fabrication of micromachine parts. Using such parts, a variety of very small functional transducers have been developed. Capacitive electromechanical transducers such as capacitive micromachined ultrasonic transducers (CMUTs) manufactured using such technology have been studied as alternatives to piezoelectric transducers. Such capacitive electromechanical transducers enable transmission and reception of ultrasound by using vibration of a vibration film, while it can easily achieve good broadband characteristics particularly in liquid.
Concerning such capacitive electromechanical transducers, Japanese Patent Application Laid-Open (JP-A) No. 2010-098454 discloses a transducer in which the parasitic capacitance between a wire connecting a plurality of upper electrodes and a lower electrode is reduced using a monocrystalline silicon vibration film formed by bonding onto a silicon substrate or other processes. According to this publication, a silicon substrate is used as a lower electrode, and upper electrodes are provided on the monocrystalline silicon vibration films. The upper electrode on each vibration film is connected to a wire, and a supporting portion of the vibration film provided between the lower electrode and the wire has a cavity so that the parasitic capacitance generated between the wire and the lower electrode is reduced.